Gastogal = Delta Belun; the planet with the floating city and origin of the emperor and his temple knights
Mizun = Juno; the last planet conquered in the second holy war; the descendent of the king of the strongest tribe there will rise up and rebel against the empire.

Some are not so easy, I think though:

Trydetol = Both; this is where the rebellion really gets going and has it's base of operations (rather than the less successful attempt in Mizun), most of the gathering of rebel forces is done around here and they seem to travel here and treat it as HQ
Koam = Addler; a backwater?

Also, Trydetol and Koam seemed kind of deserty or savannah like, compared with Mizun's jungle which seems to fit the FSS equivalents.

I have no idea what the 5th planet in L-Gaim is though. All five are mentioned as Giwaza says that if he destroys Gastogal there are still four more planets, so I don't think that the 5th was destroyed like Kallamity Goddarce. Also, nothing of Stant.